package com.roger.springcloudGreenwich.service;

import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.stereotype.Service;

import java.time.LocalDateTime;
import java.time.ZoneOffset;
import java.time.format.DateTimeFormatter;

@Service
public class RedisIdGenerator {


    /**
     * 开始时间戳
     */
    private static final long BEGIN_TIMESTAMP = 1640995200L;

    /**
     * 序列号的位数
     */
    private static final int COUNT_BITS = 32;


    private final RedisTemplate<String, Long> redisTemplate;

    public RedisIdGenerator(RedisTemplate<String, Long> redisTemplate) {
        this.redisTemplate = redisTemplate;
    }

    @SuppressWarnings("ConstantConditions")
    public long nextId(String keyPrefix) {
        // 1. 生成时间戳
        LocalDateTime now = LocalDateTime.now();
        long nowSecond = now.toEpochSecond(ZoneOffset.UTC);
        long timestamp = nowSecond - BEGIN_TIMESTAMP;
        // 2. 生成序列号
        // 2.1 获取当前日期，精确到天
        String date = now.format(DateTimeFormatter.ofPattern("yyyy:MM:dd"));
        // 2.2 获取redis自增长值
        long increment = redisTemplate.opsForValue().increment("id:" + keyPrefix + ":" + date);

        // 3. 拼接并返回
        return increment << COUNT_BITS | timestamp;
    }
}
